And now, we head overseas and to the heart of the conflict in the middle east. Israel unleashing the biggest assault on gaza yet. And for Israelis, a new look at one source of fear. Those tunnels, where Palestinian fighters emerge on Israeli soil from under the ground. ABC's David Wright is in gaza tonight. Reporter: Tonight, new video show what hamas says are fighters rising up out of tunnels, to mount a brazen attack yesterday. On an Israeli outpost. Their faces blacked out, we see them engage in a firefight. Killing five soldiers. The group's shadowy military leader pledging, no cease-fire until Israel lifts its blockade of gaza. This, after the heaviest night of bombardment so far. Israel backing up its threat to destroy hamas. Flares lit up many of the targets. One of them -- the port right outside our windows. The blast so powerful, our whole building shook like an earthquake. More than five hours of sustained shelling. A time lapse camera was stationed. From 4:00 A.M. To 5:00 A.M., a whole neighborhood reduced to rubble. This afternoon, we cautiously ventured out. This is gaza's only power station, still burning hours later. And they estimate it will be out of commission for at least a year. We also went to the home of the former Palestinian prime minister. Not anymore. The house, flattened. He wasn't home. The neighbor across the street told me Israel fired three warning shots before finally taking it out. Your whole family was able to get out? "Yes," he said, "All safe. "Tonight, renewed shelling. Two sides very much at war. Neither backing down. David Wright, ABC news, gaza.

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